Journalist Bishop is a Texan. But, he hastens to note, he lives in an Austin suburb that gave more votes to Nader than Bush in the last election and where the lone “out” Republican is a very lonely man. The mores of the neighborhood encourage political discussion, though only of a like-minded kind. The watershed year was 1965, before which Americans were used to the thought that people of different races, incomes, religions and voting habits might live more or less side by side. Afterward, Bishop observes, through white flight and minority migration, whole cities were remade to be monoethnic, with even income distributions and similar levels of education, some higher and some lower. Thus the fact that in 1970 only 17 percent of the residents of Austin were college-educated, a number that had risen to 45 percent in 2004, whereas in Cleveland “the change was only from 4 percent to 14 percent.” All other things being equal, a liberally inclined college-educated person chose Austin, Portland or San Francisco over any of the old Rust Belt cities, even if the cost of living were substantially lower in the latter. Just so, in those few surviving mixed cities where red- and blue-state types come together, they’re likely to do so only tangentially but live in neighborhoods that are more alike than unlike. The loss of diversity is of interest to more than just marketers, who have a lot of rethinking to do about demographics and target audiences, since “there is no longer national ‘brand loyalty’ in regard to religion,” much less sandwich spread or laundry soap. Instead, by Bishop’s account, this sorting tendency is of concern: We’ve cleansed our personal spaces of heretics but removed all the grit and tumult that make for debate and democracy, which spells trouble ahead for the republic.